Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 472 CRUSTACEA. A' of the second pair are by far the largest; they are moved more or less outwards and are provided with a very large chela. The three following pairs resemble each other in size and structure, each ending in a smaller rounded chela. Accordingly there remain for locomotion only the three pairs of legs of the last three uncovered thoracic segments; they have the form of biramous swimming feet. The abdominal swimming feet, however, are much more developed and bear the branch
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 472 CRUSTACEA. A' of the second pair are by far the largest; they are moved more or less outwards and are provided with a very large chela. The three following pairs resemble each other in size and structure, each ending in a smaller rounded chela. Accordingly there remain for locomotion only the three pairs of legs of the last three uncovered thoracic segments; they have the form of biramous swimming feet. The abdominal swimming feet, however, are much more developed and bear the branchial tufts on their external lamella?. The two sexes are only slightly different. The male is, however, easily to be recognised by the possession of the pair of rods at the base of the last pair of thoracic feet, and also by the slightly modified form of the first pair of abdominal feet. Me tarn orphosis.—The post - embryonic development consists of a complicated metamorphosis, which, unfor- tunately, is as yet not com- pletely known to us. The youngest larvae observed (about 2 mm. long) already possess all the segments of the tho- rax ; but the abdomen, except the caudal plate, is still un- developed. They are thus very different from the Zoa?a of the Decapod a. Later larval stages are described as Alima and Erichthus (fig. 370). The Stomatopoda are found exclusively in the warmer seas. They are excellent swimmers and live by preying on other marine animals. Fam. Squillidse. SquiHa -mantis Bond., Sq. Drx-marcst'ii Risso, Adriatic and Mediterranean. (3) Sub-order: Schizopoda.* Siiudl Thoracostraca with large, usually soft cephalo-thoracic shield and eight pairs of biramous thoracic feet, which are similarly formed and frequently bear freely-projecting gills. * G. 0. Sars, ' Hist, nat. des Crustace's d'eau douce de Xorvege,' Christiania, FIG. 370.—Young Alima larva. Af. Abdominal feet (pleopods); Mxf', anterior maxillipeds ; Mxf, the large maxillipecls (second pair).
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